Officials at the Arlington Heights Senior Center say it's rare there's a waiting list for informational events there, but one session on the Affordable Care Act is expected to pack the house.

A forum on the federal law—one aspect of which recently went into effect—is scheduled for Oct. 8 at the senior center, 1801 W. Central Road, but has already hit capacity with 125 people registered to attend, officials said.

"This is an exceptionally large attendance for a lecture-style session," said Karen Hansen, the center's manager, of the event, which will be presented by the Alexian Brothers Medical Center. "The importance of the topic – there's changes that are coming into place."

The law's latest milestone is expected to affect thousands in Cook County.

This week, thousands of Cook County residents got new health care options through the state's online "marketplace" for insurance plans. Uninsured residents were allowed to begin shopping different coverage options, from which they would be required to select by March 31 to avoid a tax penalty. The insurance marketplace opened Tuesday to a mix of excitement, confusion and concern.

To brace for the sweeping changes, state and local agencies rolled out broad initiatives to help consumers navigate the new options.

Officials with the Cook County Health System set a goal of enrolling 115,000 residents in CountyCare, an Illinois Medicaid program for adults, before the Tuesday debut of the Affordable Care Act marketplace, spokeswoman Marisa Kollias said. By late last week, about 103,000 eligible adults between the ages of 19 and 64 had already been enrolled in the program, which will provide a bridge for low-income residents to the new federal health care program, she said.

"A lot of folks in the county need health insurance, so we've had a major outreach program running since last winter," Kollias said. "We've already had great success helping a lot of uninsured residents get high quality health care."

Kollias there are currently an estimated 750,000 uninsured Cook County residents, which officials expect will drop to roughly 500,000 residents with the start of the Affordable Care Act. That number will also decline as residents continue to enroll in health insurance programs, she said.

In order to be covered by Jan. 1, the uninsured will need to enroll by Dec. 15.

Alison Leipsiger, legislative director for state Rep. Daniel Biss, D-Evanston, said counselors will be on hand to assist residents with questions about the Affordable Care Act and health-care transition at a public forum on Sunday, Oct. 13, at Evanston's Levy Center.

Biss and other state officials will lead a discussion on the new health care program, Leipsiger said.

"The truth is, we're hearing from a lot of people who are unsure of whether the Affordable Care Act will affect them, whether they're a small business owner or someone with coverage through their employer," Leipsiger said. "They have a lot of questions, and we're excited to help our constituents."

Not everyone's convinced the new law will be a boon for all.

Dean Klassman, a health insurance broker for more than 30 years, said young and healthy people might pay more than they otherwise would in a given geographic area because of the community rating rules of the new law.

"That's the scary part," said Klassman, of the Arlington Heights-based Klassman Financial Services.

Under the new law, no longer will people with pre-existing conditions be denied access to health insurance or have to pay exorbitant rates.

That sounds good to Will Wilson, 59, a Highland Park man who was diagnosed with AIDS about 10 years ago. When Wilson learned of the Lake County education initiative, he raised his hand to become one of the Moraine Township's volunteer in-person counselors.

Formerly a graphic designer, Wilson says he's had to take low-paying jobs in the past to remain eligible for the AIDS Drug Assistance Program, the state's Ryan White program that helps low-income people with HIV/AIDS afford the expensive medication. Wilson's medicine costs about $3,700 a month, he said.

Now he'll be able to find seek a full-time job or find an insurance plan without fear of being denied coverage for the pre-existing condition.

"If I had to use one word, it would be 'freedom,' " Wilson said.

But even in that example, there are some uncertainties.

It's not clear at this point how a new insurance plan purchased through the marketplace will interface with the state programs – Ryan White and ADAP – for people with HIV, Wilson said. So he may wait to enroll until that becomes clearer.

The Arlington Heights event is just one sign that the roll-out has many thirsting for knowledge.

The popular, 42,000-square-foot senior center estimates it already gets about 500 visitors who drop in each day, so attendance for the Affordable Care Act event was capped because of parking concerns, officials said.

The event will go over the impact of the law, how it will relate to Medicare for seniors and the future of health care for all, officials said. As of late September, there were about a dozen people on the waiting list.